The present invention relates to a thiocarbonylthio compound, and more particularly to a radical polymerization process for preparing polymers of vinyl monomers with controlled molecular weight and narrow polydispersity in the presence of the thiocarbonylthio compound.
Radical polymerization is one of the most widely exploited polymerization processes in industry due to the variety of the polymerizable monomers (such as styrenes, acrylates, methyl methacrylates (MMA) or acrylonitrile (AN)), relatively simple reaction conditions. In conventional radical polymerization, however, it is difficult to control the size of the polymer chains and the molecular mass distribution. The polymers thus prepared contain chains of very large and very small masses (broad polydispersity), and this results in materials with uncontrolled properties.
The traditional living cationic and anionic polymerization methods can be used to control the degree of polymerization for specific monomers and obtained narrow distribution of molecular weight. However, they are limited in their ability to precisely modify the configuration of polymer products. As well, the variety of monomers applied to the above polymerization methods is limited, and strict reaction conditions thereof also restrict use in related applications.
In 1998, CSIRO disclosed a living free radical polymerization method called reversible addition-fragmentation chain transfer process (RAFT process) to prepare polymer products with narrow molecular weight distribution and further control the polymer chain length. The so-called RAFT process is a combination of general procedures for traditional free radical polymerizations with the addition of a reversible addition-fragmentation chain transfer reagent (RAFT reagent). The conventional RAFT reagents are difficult to prepare and have high cost, due to complex preparation and purification steps.
Therefore, it is necessary to develop a novel radical polymerization process.